Semiconductor device test probe having improved tip portion and manufacturing method thereof

ABSTRACT

A semiconductor device test probe having a tip portion for being urged against an electrode pad of an integrated semiconductor device to establish an electrical contact against the electrode pad for testing functions of the semiconductor device. The spherical tip portion has a radius of curvature r expressed by 8t≦r≦23t, where r is the radius of curvature of the spherical surface and t is the thickness of the electrode pad. The tip portion may have a first curved surface substantially positioned in the direction of slippage of the probe when the probe is urged against the electrode pad and slipped relative to the electrode pad and a second curved surface opposite to the first curved surface. The first curved surface has a radius of curvature of from 7 μm to 30 μm and larger than that of the second curved surface. The test probe may be manufactured by a method comprising the steps of roughing the tip portion of the curved surface by abrasing by means of electrolyte abrasion or abrasing particles to form a symmetrical spherical curved surface, and finishing the tip portion by sliding it on an abrasive member comprising an elastically deformable thick film fixed to a substrate and having abrasive particles therein or thereon directly or through a metallic film.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Application No. 10-245881, filed in Japanon Aug. 31, 1998 and Application No. 11-241690, filed in Japan on Aug.27, 1999, the contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

This invention relates to a semiconductor device test probe,manufacturing method therefor and a semiconductor device tested by suchthe probe.

With the conventional test probe as shown in FIG. 13a, the testing(probing) is carried out by attaching a probe 202 having a for and bentinto a hook-like shape to a probe card 201 which is vertically movable,and pushing the probe 202 against a test pad of a semiconductorintegrated circuit (referred to as an electrode pad herein after) insuch a manner than an oxide film on the pad surface is broken off toestablish true contact (electrical contact) between the probe and afresh surface of the pad. The condition of a probe tip under the probingis shown in FIG. 13b. For the sake of easy understanding, FIG. 13b isillustrated in the form of a simplified model with respect to dimensionsand the like. As shown in FIG. 13b, the tip 200 of the conventionalprobe is originally finished to have a flat end face, so that at thetime of probing the whole of the flat tip portion is brought intocontact and an oxide film 204 and contaminants on the surface of theelectrode pad 203 are left interposed between the probe tip and the padsurface.

Further pressing of the probe against the electrode pad to drive it by50-100 μm further downward (overdrive) causes the inclined tip of theprobe to slip and break a portion of the oxide film 204 to make theconducting portion 206 through which an electrical true contact isestablished, permitting the conduction test to be achieved. At thistime, the probe is slightly rotated by flexure. Therefore, in a probecard having a number of probes with a flat finished tip, an angle of theflat surface at the probe tip portion is not equal to each other duringthe overdriving, thus posing a problem that the contact state is notstable.

Also, in Japanese Patent Laid-Open No. 6-61316, an example is disclosedin which the tip of the probe is formed into a sphere-shape or an ovalsphere-shape in order not to damage the electrode pad of the integratedsemiconductor device. In this example, differing from the one in whichthe tip portion is finished flat, any problem due to the deviation ofthe contacting surface areas does not arise.

Japanese Patent Laid-Open No. 8-166407 discloses an example of a probefor testing lead portions (final test) of a semiconductor device,wherein the radius of curvature r of the tip portion of the probe ismade from 0.5R to 5R (R is the diameter of the tip portion of theprobe), whereby the contacting area becomes more stable as compared tothe case where the tip portion is flat for the reasons the same as thatfor the foregoing spherical tip portion, thereby to suppressing thetemperature rise of the probe and preventing the welding of Sn. Here,the minimum radius of curvature is set at the machining limitation or tobe a semi-sphere shape. Also, the reasons for the maximum limit of 5R isexplained to be for the purpose of preventing the ridge defined betweenthe side portions and the spherical tip portion from planing the platedSn.

Japanese Patent Laid-Open No. 5-273237 discloses a structure forbringing the tip of the probe into a line contact with an electrode pad.According to this paper, even if the electrode pad is small, the probedoes not fall off from the pad, allowing an accurate measurement, sothat the tip portion may preferably have the shape as shown in FIG. 14.

Further, Japanese Patent Laid-Open No. 8-152436 discloses an example asshown in FIG. 15 in which the probe comprises a first surface 207 thatbecomes parallel to the pad surface when the tip of the probe is broughtinto contact with the semiconductor pad and a second surface 208 that isparallel to the pad surface during the test. According to this probe,the first surface 207 causes an oxide film on the electrode pad toseparate to expose the surface without the oxide film, thereby to ensurethe good contact state. The second surface is three times larger thanthe first surface, ensuring the sufficient contact surface area.

Also, since tungsten used as the probe material is made of sinteredpowder material, the finishing of the tip shape is often achieved by theelectrolytic abrasion, but since agglutination can easily take placewhen the surface coarseness is large, the forgoing Japanese PatentLaid-Open No. 8-166407 proposes a measure for decreasing the surfacecoarseness by selecting a suitable electrolytic conditions. Also, theeffectiveness of polishing the tip into a mirror surface is disclosedalso in Japanese Patent Laid-Open No. 8-152436.

Since the conventional probe is constructed as above and the truecontact area between the tip portion of the probe and the electrode padat the time of test (electrically conductive portion 206) is extremelysmall, a sufficient conduction was some times not properly provided.Also, the repeated probing causes the oxide films 204 to build up on thetip portion 200 of the probe, the true contact surface area relative tothe electrode pad is decreased, making the electrical conductionunstable.

Also, even though the stress may be decreased by making the tip portionspherical, the oxide film cannot sufficiently be removed, so that asufficient true contact surface area cannot be maintained. That is, evenwhen the contact surface is made large, the remains of the aluminumoxide film immediately below the spherical surface impedes the stablecontacting and it is necessary to rather frequently remove the aluminumoxide that attaches to the tip portion as the number of times ofcontacts increase.

In the structure for achieving the separation of the oxide film and theestablishment of a true electrical contact by different respective tipsurfaces such as shown in FIG. 15 which is an arrangement suggested tosolve the problem of residual oxide film, it was found that, while goodresults were obtained at the initial state, some probes generate poorcontacts as the number of times of contacts increases. As a result ofthe observation and the analysis of the state of the probes inconnection with this problem, it was found that when the second contactsurface is brought into contact with the electrode pad and repeat thistest several times, the second contact surface has aluminum attachedthereto, which increases the contact resistance when oxidized. The aboveassumption is considered reasonable from the fact that this phenomenongenerated more often after the exchange of the semiconductor wafer andthe halt of the line, i.e., when the test is interrupted for more thanseveral minutes. It is considered that the reason some probes generatedpoor contacts and some other did not is because the contact surfaceshave different from angles in view of the fact that the number of probesare simultaneously brought into contact with the electrode pads, so thatit is difficult in the arrangement shown in FIG. 15 to work the firstand the second flat surfaces to precision and posed problem in multi-pinmeasurement which will be more often required in the future.

Another problem was that aluminum which is the electrode materialpenetrates into polishing scars generated during the probe surfacepolishing and this aluminum oxides to cause improper contact. It wasalso found that, since the tungsten probe material has cavity holestherewithin because of it being a sintered body, aluminum enters intothe cavities and oxidize, leading to a poor contact.

Also, when the wire bonding is achieved to the semiconductor deviceafter it is tested by the probes, the probe trace causes the yield ofthe bonding to be decreased. Particularly, when the electrode pad ismade small and at the same time the bonding size is made small to makethe semiconductor device small in order to increase the number ofsemiconductor device taken per one wafer, the size of the probe trace isdesired to be small which disadvantageously affects the electricalcontact, resulting in that the bonding yield was decreased.

The chief object of the present invention is to provide a new andimproved semiconductor device test probe free from the above discussedproblems of the conventional test prove.

An object of the present invention is to provide a semiconductor devicetest probe in which the true contact surface area between a probe tipportion and an electrode pad can be increased and a sufficient reliableelectrical connection with a minimum probe sliding amount can beestablished.

Another object of the present invention is to provide a semiconductordevice test probe which is maintenance free in the sense that electrodematerial does not stick to it.

A further object of the present invention is to provide a method formanufacturing a semiconductor device test probe for manufacturing a testprobe in which the true contact surface area between a probe tip portionand an electrode pad can be increased and a sufficient reliableelectrical connection with a minimum probe sliding amount can beestablished.

Another object of the present invention is to provide a manufacturingmethod for a semiconductor device test probe which is maintenance freein the sense that electrode material does not stick to it.

A still another object of the present invention is to provide a methodfor manufacturing a semiconductor device test probe for manufacturing atest probe in which the true contact surface area between a probe tipportion and an electrode pad can be increased and a sufficient reliableelectrical connection with a minimum probe sliding amount can beestablished.

Another object of the present invention is to provide a reliablesemiconductor device tested by the probe of the present invention.

SUMMARY OF THE INVENTION

With the above objects in view, the present invention resides in asemiconductor device test probe having a tip portion for being urgedagainst an electrode pad of an integrated semiconductor device toestablish an electrical contact between the tip portion and theelectrode pad for testing a function of the semiconductor device. Thetip portion defining a spherical surface has a radius of curvature rexpressed by 9t≦r≦35t, where r is the radius of curvature of thespherical surface and t is the thickness of the electrode pad.

The tip portion defining a spherical surface may have a first curvedsurface substantially positioned in the direction of slippage of theprobe when the probe is urged against the electrode pad and slippedrelative to the electrode pad and a second curved surface opposite tothe first curved surface. The first curved surface has a radius ofcurvature of from 7 μm to 30 μm and larger than that of the secondcurved surface.

The semiconductor device test probe may be manufactured by a methodcomprising the steps of roughing the tip portion of the curved surfaceby abrasing by means of electrolyte abrasion or abraising particles toform a symmetrical spherical curved surface, and finishing the tipportion by sliding it on an abrasive member comprising an elasticallydeformable thick film fixed to a substrate and having abrasive particlestherein or thereon directly or through a metallic film.

The surface roughness of the tip portion of the probe may be equal to orless than 0.4 μm.

The tip portion of the probe may comprise fine grooves extending in thedirection of scrub of said probe against said electrode pads.

The method for manufacturing the semiconductor device test probe maycomprise the steps of working curved surface of the tip portion into asubstantially spherical curved surface by abrading by means ofelectrolyte abrasion or abraising particles to form a symmetricalspherical curved surface, and inserting or moving the tip portion intothe abrasive particles or on a resin including the abrasive particles toform fine grooves extending in the direction of scrub of the probeagainst the electrode pads

The probe may be made of a metallic material made from a powderymaterial, and the probe is heat treated, the heat treatment conditionsbeing a non-oxidizing atmosphere, at the treatment temperature of equalto or less than the recrystallization temperature of the metallicmaterial and the non-oxidizing gas is pressurized.

The present invention also resides in a semiconductor device tested bythe above semiconductor device test probe, wherein the test is achievedby urging the probe against the electrode pad of the semiconductordevice, providing a relative sliding movement between the probe and theelectrode pad to expel the electrode pad material by making a laminationstack.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more readily apparent from thefollowing detailed description of the preferred embodiments of thepresent invention taken in conjunction with the accompanying drawings,in which:

FIG. 1a is an explanatory view showing the state of the prove and theelectrode pad of the first embodiment of the present invention;

FIG. 1b is an explanatory view showing the contour of the curve surfaceof the tip portion of the probe of the first embodiment of the presentinvention;

FIG. 2 is an explanatory view showing the state of the probe and theelectrode pad of the first embodiment of the present invention;

FIG. 3 is an explanatory view showing the probe trace on the aluminumelectrode pad formed by the probe of the first embodiment of the presentinvention as compared to the case where a general probe was used;

FIG. 4 is an explanatory view showing the probe trace on the aluminumelectrode pad formed by the probe of the first embodiment of the presentinvention as compare to the case where a general probe was used;

FIG. 5a is an explanatory view showing the contact stability when theprobe of the first embodiment of the present invention was used;

FIG. 5b is an explanatory view showing the contact stability when atypical example of a conventional probe was used;

FIG. 6a is an explanatory view showing the probe prior to rounded;

FIG. 6b is an explanatory view showing the probe abraded by theelectrolytic liquid;

FIG. 6c is an explanatory view showing the probe being polished;

FIG. 7 is a graph showing the relationship between the radius ofcurvature of the probe of the first embodiment of the present inventionand the number of times of contact;

FIG. 8 is a graph showing the relationship between the surface roughnessof the probe of the second embodiment of the present invention and thenumber of times of contact at which the contact resistance exceeds 1ohm;

FIG. 9a is an explanatory side view of the probe of the third embodimentof the present invention;

FIG. 9b is an explanatory bottom view of the probe of the thirdembodiment of the present invention;

FIG. 10 is a graph showing the relationship between the surfaceroughness of the probe of the third embodiment of the present inventionand the number of times of contact achieved until the contact resistanceexceeds 1 ohm;

FIG. 11a is a diagrammatic illustration of the results of the SEMobservation of the probe according to the third embodiment of thepresent invention, wherein the radial grooves are provided;

FIG. 11b is a diagrammatic illustration of the results of the SEMobservation of the probe according to the third embodiment of thepresent invention, wherein some of the grooves are parallel to eachother;

FIG. 11c is a diagrammatic illustration of the results of the SEMobservation of the probe according to the third embodiment of thepresent invention, wherein the concentric grooves are provided; and

FIG. 11d is a diagrammatic illustration of the results of the SEMobservation of the probe according to the third embodiment of thepresent invention, wherein the grooves are randomly oriented;

FIG. 12a is a diagrammatic illustration of the results of the SEMobservation of the typical tungsten probe;

FIG. 12b is a diagrammatic illustration of the results of the SEMobservation of the tungsten probe after the heat treatment according tothe present invention;

FIG. 13a is an explanatory view of the conventional probe device;

FIG. 13b is an enlarged view of the tip of the conventional probe shownin relation to the electrode pad;

FIG. 14 is an explanatory view illustrating the conventional probe; and

FIG. 15 is an explanatory view illustrating another conventional prove.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1a, 1 b and 2 illustrates the probe 1 and the electrode pad 2,which is a film of Al—Cu of a thickness of the order of 0.8 μm for atypical logic integrated semiconductor device such as DRAM. Theelectrode pad may be 2-3 μm for a special purpose semiconductor devicesuch as a power device. The reference numeral 3 shows the crystallineorientation of the electrode pad, 4, 5 and 6 are slip surfaces, 7 atangent vector of the probe tip, 8 an oxide film on the electrode padsurface, 9 an oxide film attached to the probe, 10 an electricallyconducting portion and 11 are sheared pieces.

As illustrated in FIG. 2, the electrical conduction portion between theprobe 1 and the electrode pad 2 can be obtained by sliding the probe 1at the time of probing on the oxide film 8 and breaking the oxide film 8on the electrode pad 2, thereby bringing the probe 1 into contact withthe fresh surface of the electrode pad 2. The probe 1 is not vertical tothe surface of the electrode pad 2, but is illustrated as being tiltedby 8 degrees, which tilt angle generates a relative slippage between theprobe 1 and the electrode pad 2. FIG. 1b illustrates a contour as viewedfrom the bottom of the probe 1, from which it is seen that the tipportion is composed of a first curved surface of a radius of curvaturer1 of which contour lines are dense and a second curved surface of aradius of curvature r2 of which contour lines are spares, these twocurved surfaces constitute a continuous spherical surface.

In the conventional technique, there was no proposition that proposessuitable configurations and materials for the probe tip by making themechanism of the phenomenon clear from the view point of deformation dueto the contact between the probe tip and the aluminum pad. Therefore, anintensive study and experiments were conducted on the process for easilygenerating the shear and for preventing the attachment of aluminum. Theshear deformation generates along the slip surface of the metalliccrystalline surface. On the other hand, the crystalline direction 3 ofthe electrode pad 2 at the time of spattering is (111) which is theso-called C-axis orientation. The angle this slip surface 4 of (111)make with respect to the electrode pad is zero degree. Also, the slipsurface 5 that has the smallest angle with respect to the electrode padsurface are (110), (101) and (011), of which angle is 35.3 degrees. Ifthe shear generates only at the angles of slip surfaces, then the shearsgenerate only at incremental angles such as 0 degree or 35.3 degrees.

However, it was determined from the experimental results that the shearsgenerate at an angle intermediate between the slip surfaces 4 and 5 andnot at incremental angles. This is believed because shears that occuralong the above slip surfaces 4 and 5 are combined and resulted in ashear 11 as shown in FIG. 2. Once a slip is generated in the directionof the slip surface 4 (0 degree), the slip pieces in this direction aresubjected to a compression force in the 0 degree and prevented fromfurther slipping from that position. Therefore, the slip in thedirection of 35.3 degrees takes place more easily than the slip in thedirection of 0 degree, so that the slip that takes place next is theslip in the direction of 35.3 degrees. When the angle θ between theprobe tip and the pad surface shown in FIG. 1a is less than 35.3degrees, the slip pieces are pushed into a narrower space, resulting inthat a further slippage is prevented. In this state, the slip in thedirection of 0 degrees is easier to take place that the slip in thedirection of 35.3 degrees, forming the slip in the direction of 0degree. Therefore, the slips of 0 degree and 35.3 degrees are repeatedlygenerated and, as a result of this combination, the shears of an angleintermediate between 0 degree and 35.3 degrees are formed.

According to an experiment in which the angle of the tangentialdirection 7 of the probe tip was changed, the angle between thetangential direction 7 of the probe tip and the electrode pad surface atwhich the above shearing can take place is from 15 degrees to 35 degreesand a stable shearing takes place at from 17 degrees to 30 degrees.Therefore, when the tip configuration of the probe tip is such that theangle defined between the tangential direction vector 7 of the probe tipand the electrode pad surface is from 15 degrees to 35 degrees andpreferably from 17 degrees to 30 degrees, the oxide film 8 on thesurface of the electrode pad can be broken and establish a good contactwith the fresh electrode pad surface to obtain a sufficient electricalconduction. The relationship between the radius of curvature r of theprobe tip and the thickness t of the electrode pad which can provide theabove discussed tangential angle can be expressed by 6t≦r≦30t and8t≦r≦23t. Such the phenomenon can be seen in common in metals of facecentered cube lattice such as Al, Au, Cu, Al—Cu alloy, Al—Si and thelike.

FIG. 3 illustrates the probe trace generated on the aluminum pad 2through the use of the probe 1. Since the aluminum 31 sheared and purgedby the probe has the laminar structure, it is determined that the probetip portion has caused the series of shearing deformations in the testpad material. The above laminar structure is laminated to have athickness (about 1.5 μm in this example) greater than the thickness ofthe aluminum pad of 0.8 μm, and the removal configuration is thatprojections are formed in front of the probe tip portion on the aluminumpad as viewed in the direction of slip of the probe, An example of aremoval configuration according to the conventional technique is shownin FIG. 4, from which it is seen that substantially no removal isachieved in the forward direction.

It is now clear from the analysis of the contact mechanism and theobservation of the removal state that the problems raised when the probetip is flat or a spherical surface has a large radius of curvature canbe explained by the following two phenomena. First, the projectionformed due to the removal of the electrode pad material in the forwarddirection as viewed in the probe slipping direction and the electricalcontact is established under or rear of the probe tip portion. However,the slip surface direction and the pressurizing direction are notcoincide under or the rear of the probe, so that the fresh surfacecannot easily be formed. That is, the oxide film remains between theneedle and the electrode pad. Therefore, by making the contact surfacearea large, an electrical contact is maintained even when the freshsurface is only a small portion. Secondly, when the fresh surface isformed, another problem of the attachement of aluminum to the proberaises. When this aluminum oxides and could not be removed at the timeof next probing, the electrical contact is improper.

On the other hand, according to the present invention, the contact angledefined between the electrode pad surface and the probe is set so thatthe slip is easily generated and the fresh surface is formed at theforward face of the probe to establish an electrically intimate contactsurface therethrough because of the force in the longitudinal directionof the probe is applied. Although aluminum attaches to this surface asin the conventional technique, it is positioned in the direction of theslip of the probe at the next probing, so that it is removed by amassive separating force applied at that time, whereby a fresh surfaceis always maintained. Accordingly, the residual aluminum is located atthe position close to the side surface of the second curved surfacewhere no electrical contact is necessary. FIGS. 5a and 5 b are graphsshowing the results of the conduction tests of the probe of the presentinvention and the conventional probe, respectively. According to thegraph of FIG. 1a, it is seen that no failure of electrical conductionoccurred even when the contact of 15000 times were carried out, whilewith the conventional probe as shown in FIG. 1b the improper contactshaving the resistance of more than 1 ohm generated even at the contactof 500th times.

According to the present invention, a trace of slip of the probe on theelectrode pad of the semiconductor device is formed and particularly thelaminar stack of removed material is formed at the forward end of thetrace. While the probe trace is formed with the conventional probe, itis desired to be smaller for the subsequent wire-bonding step. Inparticular, for the smaller semiconductor devices, the electroniccircuitries are highly integrated and the wiring pattern width as wellas the electrode pads is getting smaller. However, it was not possibleto make the probe trace smaller with the conventional probe because thereliability of the electrical contact becomes worse. This is because theelectrical contact is established at the bottom surface of the probetip. Therefore, it has been necessary for the probe trace to have awidth of the order of 20 μm and a length of the order of 40 μm (seeFIGS. 3 and 4) and, when the contact is not stable, the probe has beenapplied for the probing to the same electrode pad, resulting in a stilllarger probe trace.

According to the present invention on the other hand, the probe tracecan be made as small as to have a width of 12 μm and a length of 20 μm.Also, the observation of the bonded portion of the wire-bonding hasrevealed that the alloy layer which is the index of the stability of thebonding on the probe trace is not sufficiently formed and that thedifference in size of the probe trace significantly affects the qualityof the wire bonding. That is, the size of the wire-bonding portion isset to be a circle of a diameter of 65 μm for an electrode pad of 80 μmat one side. For the compact semiconductor device in the future, the oneside of the electrode pad should be 65 μm and the bonding area shouldhave a diameter of about 55 μm. The area of the probe trace was 800 μm²for the conventional probe and 240 μm² for the probe of the presentinvention, so that the probe trace according to the conventional probeis sufficiently large in comparison with the bonding area of 2400 μm²for the small electrode pad (55 μm diameter) to deteriorate the qualityof bonding, whereas in the present invention in which the probe tracearea is 240 μm² which is about ⅓ of that according to the conventionalprobe, generating no deterioration in bonding. For a small electrode padand particularly in the long-term reliability, about 5% of the probetraces were improper in poor opening with the conventional probe,whereas in the present invention there were no failure.

If the radius of curvature of the probe tip is made small, the pressureapplied to the electrode pad becomes high and generates damages (cracks)to the electrode pad. Usually, the probe is pressed against thesemiconductor device with a force of the order of 7 gf and, if the forceis decreased to 3 gf for example in correspondence with the reducedcontact surface area, the poor contact was formed. This is because theconventional probe is designed so that a sufficient electricalconduction can be established even when the fresh surface is small dueto the deviation. With a small contact surface area, the fresh surfacearea is also small and fluctuated in relation thereto, resulting in thepoor contacts. Therefore, it was determined that the arrangement of theprobe is effective for the prevention of the damages to the electrodepad in which, as in the present invention, the front of the probe asviewed in the direction of slip of the probe is configured for an easyformation of the fresh surface of the electrode pad (a spherical curvedsurface of a radius of curvature r1), while the area of the bottomsurface (a spherical curved surface of a radius of curvature r2) out ofthe front surface and the bottom surface for supporting the probepressure is made large. That is, in the present invention, theelectrical contact is ensured at the front surface or the first curvedsurface and the stress is decreased by the bottom surface or the secondcurved surface. At that time, since the arrangement is such that theprobe slightly flex and rotate by the overdrive to make thee contactsurface area at it maximum at the time of overdrive completion at whichthe probe pressure is the highest, the pressure applied to the electrodepad can be lowered.

Also, by making the tip portion spherical, the contacting surface areais advantageously stable differing from the flat surface heretoforeproposed even when the height of the individual probes is different(usually deviation of 10 μm or so is observed). The final load appliedto the probe when the probe is pushed by a predetermined amount ofover-drive can be set at a desired value by suitably selecting thethickness or length of the probe. However, the load inevitably increasesas the over-drive progresses. Since the present invention is arrangedsuch that contact area between the probe tip and the electrode padincreases as the progress of the over-drive, the pressure applied to thesemiconductor device does not increase even when the height of the probehas deviation, whereby the damages to the electrode pad can beprevented.

It is to be noted that while the tilt angle of the probe 1 is made 8degrees in the above conduction tests, the angle for the typical probeis of the order of 6 degrees, and a good result can be expected withregard to the contact stability even with this angle. However, it isdesirable to make the tilt angle larger in order to prevent the damagessince the contact area is limited to be small in the present inventionand, taking the dislocation of the probe from the electrode pad 2 intoconsideration, the preferable tilt angle is within a range of from 8degrees to 12 degrees.

The above-described first curved surface and the second curved surfacecan be easily formed at the tip portion of the probe by the novelmanufacturing method as described below in conjunction with FIGS. 6a to6 c. In FIG. 6a, a rod material 1 a of the probe 1 is dipped at its tipinto an electrolyte liquid 12 to form the probe having a substantiallyaxially symmetrical spherical surface at its end as shown in FIG. 6b.Alternatively, the Si abrasive particles may be used to forma thespherical surface. Then the probe 1 is further polished or finished byan abrasion device shown in FIG. 6c to have a first curved surface of afirst radius of curvature and a second curved surface of a second radiusof curvature smaller than the first radius of curvature to form anaxially asymmetric curved surface. The abrasion device may have anelastically deformable thick film of abrasive material, such as a filmcontaining abrasive therein, a film having the abrasive attached on thesurface or elastic deformable thin film attached through a metallicfilm. It is seen that the abrasion device shown in FIG. 6c comprises abase member such as a silicon substrate 13, an elastic layer such as apolyimide sheet 14 attached to the silicon substrate 13, a thin Ti film15 disposed on the polyimide sheet 14 and an abrasive material layer 16such as TN film formed on the Ti film 15. The polyimide layer 14 mayhave a thickness of 50 μm and may be made by coating or bonding. The Tifilm 15 may be 100 Å thick and the TiN film may be 24 μm. Alternatively,a thick resin layer containing Si abrasive particles having a thicknessof 300 μm for example may be directly attached to the silicon substrate13 and used as the abrasive material.

In order to polish the spherical tip portion of the probe 1, the probe 1is attached to the probe card and pressed against the abrasive material16 under pressure and repeatedly moved up and down with an over-driveamount, such as several 100 μm, greater than the over-drive amount atthe time of the wafer test. The tip of the probe attached to the probecard at an angle therewith is forced to make a sliding movement alongthe abrasive member due to the vertical movement of the probe card. Theprobe tip portion is embraced by the elastically deformed abrasive toallow the second curved surface having the second radius of curvature r2to be formed. The radius of curvature r2 can be adjusted by thethickness of the abrasive member and the elasticity. When the probe maybe first moved along the surface for a predetermined distance after itis brought into contact with the abrasion device and then moved back andforth about this new position on the abrasion device, the second curvedsurface can be more selectively polished.

The abrasion member may be made by directly securing the abrasivematerial to a low-rigidity material attached to a high-rigiditysubstrate or by securing a thick resin film of low rigidity andcontaining abrasive material to a rigid substrate instead of theabove-described material and structure. It should be noted that theprobe should be able to move on the abrasion device with the surface ofthe device slightly elastically depressed or penetrate into the abrasivematerial during the movement or, preferably, the probe slides along thesurface of the elastic abrasive member, whereby the tip portion caneasily be provided with a surface having a different radius ofcurvature.

The contact stability is significantly changed according to whether ornot the shear deformation of the electrode pad can be easily generatedeven with the same spherical surface. FIG. 7 illustrates the testresults of contact lifetime against various radius of curvature with anelectrode pad of 0.8 μm thickness of a typical integrated semiconductordevice such as a DRAM. It is seen from the graph that good results ofthe contact life time can be obtained with the radius of curvature offrom 7 to 30 μm, preferably from 10 to 20 μm. The radius of curvature ofequal to or less than 7 μm is too small to transmit a sufficient forceto the first surface of the electrical conduction surface and thesurface area is small, and the upper limit of from 20 to 30 μmsubstantially coincide with the upper limit of 24 μm where the shear ofthe electrode pad generate.

While the thickness of the electrode pad changes, the suitable radius ofcurvature r1 also changes accordingly and the radius of curvature r1should satisfy

9t≦r1≦35t

While the probe tip portion of the present invention has been describedas being a spherical surface for an easy explanation of the relationshipbetween the angle of slip in which the shearing deformation of theelectrode pad takes place, the tip portion may not be a perfect sphereand a similar results can be obtained with a curved surfaceconfiguration close to a sphere.

Also, while the Al—Cu alloy has been explained as an example of the testpad material, the similar advantageous results can be obtained when theelectrode pad material is aluminum, Al—Si—Cu alloy, copper or the likewhich exhibits sip deformation (shear deformation) similar to that ofaluminum.

FIG. 8 is a graph showing the relationship between the surface roughnessof the probe of another embodiment of the present invention and thenumber of times of the contact, the test being conducted on a DRAM ofwhich electrode pad having a thickness of about 0.8 μm with a probehaving a radius of curvature of tip portion of 15 μm. From the graph, itis seen that when the surface roughness is as high as 1 μm the life isabout 20,000 times of contacts, whereas when the surface roughness islowered by the electrolytic abrasion for example, the number of thecontact times is abruptly increased when decreased to or below 0.4 μm.Particularly, the number of contacts reached as high as 380,000 times at0.1 μm, which is about 20 times higher than that when the surfaceroughness is 1 μm. The reason for this is considered that it becomesdifficult for the oxide to attach to the tip of the probe, and similarresults were obtained even when the thickness of the electrode pad orthe radius of curvature of the probe tip is changed within the rangeindicated in the above-described first embodiment.

FIG. 9a is an explanatory side view of the probe of the third embodimentof the present invention and FIG. 9b is an explanatory bottom view ofthe probe shown in FIG. 9a. In the figures, the probe 1 has at its tipportion a plurality of radial grooves 17. As in the above secondembodiment, the surface of the probe having a radius of curvature of 15μm is finished at various surface roughness and the grooves 17 which areabrasion scratches extending from the center of the probe in the radialdirection through the use of abrasion particles. Such the probes wereused in the test of DRAM's of which electrode pad are about 0.8 μm. FIG.10 is a graph showing the relationship between the surface roughness ofthe probe of the third embodiment of the present invention and thenumber of times of contact achieved until the contact resistance exceeds1 ohm, also showing for comparison purpose the data of the probe (brokenline) to which only a typical abrasion is achieved and random-orientedscratches are formed. It is seen from the graph that the probe havingradially extending grooves is significantly higher number of times ofcontact as compared with a typical probe simply polished. The reason forthis is considered that, when the probe is pressed and scrubbed againstthe electrode pad, the metal such as aluminum of the electrode padplastically flows along the radially extending grooves withoutmechanically engaging at the random scratches or step-like portions dueto the abrasion scratches, whereby the chance of the pad metal such asaluminum attaches to the tip portion of the probe and oxidizes toincrease the contact resistance is increased.

In order to confirm the above phenomenon, various probes with groovesmanufactured with abrasive of 5 μm grain size in various condition areurged against the electrode pad of the DRAM's and observed by a scanningelectron microscope (SEM). FIG. 11a is a diagrammatic illustration ofthe results of the SEM observation of the probe 1 according to thepresent invention wherein some of the radial grooves 17 have attachedthereto attachments 18. In FIG. 11b, some of the grooves 17 b positionedat least at the position brought into contact with the electrode pad aremade parallel to each other. In FIG. 11c, the probe 1 has concentricgrooves 17 c, and in FIG. 11d the probe 1 has grooves 17 d that arerandomly oriented. When these probes 1 are urged against the electrodepad in the direction indicated by a white arrow, some attachments 18which are believed to be aluminum or its oxide are observed as shown inthe figures. It is understood from these observations that muchattachment of aluminum or its oxide is observed on the probes shown inFIGS. 11c and 11 d and a very small amount of attachment of aluminum orits oxide is observed on the probes shown in FIGS. 11a and 11 b and thatthe attachment to the probes can be prevented by forming the scratchesor grooves 18 substantially along the direction of movement of thescrubbing.

In order to form grooves substantially parallel to the direction ofscrubbing on the tip portion of the probe, the tip portion is firstworked by the abrasion using an ordinary electrolyte liquid or Siabrasion grains into a desired spherical shape. Then, in order to formthe grooves in radial direction, the probe is inserted in thesubstantially vertical direction into the abrasion grains, or asubstrate or a film in which the abrasion grains are embedded within aresin such as polyimide. Alternatively, in order to form the parallelgrooves, the probe is moved on the abrasion grains, or on the film inwhich the abrasion grains just mentioned above are embedded or asubstrate on which an abrasion material film is formed. The abrasiongrains used may be Si, SiC, Artificial diamond or the like, and shouldpreferably have the grain size of equal to or less than 5 μm in order toform the grooves of the above embodiments. Also, the film into which theabrasion grains are embedded may be manufactured by mixing the abrasiongrains in the resin and by securing.

FIG. 12a is a diagrammatic illustration of the results of the scanningelectron microscope (SEM) observation of the system of the typicaltungsten probe and FIG. 12b is a diagrammatic illustration of theresults of the scanning electron microscope (SEM) observation of thetungsten probe after the heat treatment according to the presentinvention. In order to collapse the voids contained in the tungstenprobe which is made of a sintered porous material, the sintered materialis rolled by machining and wire-drawn into a wire to provide needlecrystalline system. The voids or cavities however still remain by 1-2%and it is therefore desirable to apply the heat treatment for collapsingthe cavities includes. However, when the heat treatment at therecrystallization temperature range for the tungsten material isachieved, the needle-like crystal system of the tungsten material isdestroyed and the probe becomes brittle to deteriorate the strength ofmaterial inherent to tungsten is deteriorated, so that it is notpossible to apply such the heat treatment to the thin probe such as thatused in the present invention. Thus, according to the present invention,a high pressure is applied to the probe from outside at a relatively lowtemperature so that the multiplier effect of temperature and pressure isutilized to collapse the cavities within the tungsten material.

The metallic material wire-drawn such as the probe has a pretty highwork strain (residual stress) within the material. Due to this workstrain, the chemical potential energy of the metal atoms arranged atrandom particularly around the crystal grain boundary. Accordingly, thismetallic material high in the work strain is heated to a temperatureequal to or less than the recrystallization temperature and put it undera hydraulic pressure from the outside to collapse the cavitiespositioned around the crystal grain boundary within the metallicmaterial. The heat treatment was achieved at a temperature equal to orless than the recrystallization temperature of the bulk material, thepressure is equal to or more than that needed to generate the slip ofthe material and the treatment time lasts until almost all of themovement of the atoms of the metallic material to be treated comes tostop. More particularly, the treatment temperature is 300° C.-600° C.,the treatment pressure is 200-2000 atms and the treatment time is 0.5 to5 hours, whereby the cavities can be decreased. I was determined fromthe experiment that the cavities are significantly reduced particularlywhen the treatment temperature is 500° C., the treatment pressure isequal to or more than 1000 atmospheric pressure and the treatment timeis equal to or more than 1 hour.

As for the pressure conditions, the processing time is shorter when thepressure is higher. While the typical cavity collapsing heat treatmentis achieved at a temperature equal to or above the recrystallizationtemperature of the material (usually a temperature 4-5 times higher themelting point of the material) and under a high pressure (referred to asHIP treatment), according to the present invention, the cavities arecollapsed by the heat treatment at a temperature one digit lower ascompared to the melting point 3,400° C. of the tungsten as shown inFIGS. 12a and 12 b. Also the brittleness of the material is notincreased as compared to the heat treatment at or above therecrystallization temperature. With a thick probe of a diameter of about5 mm, the above heat treatment with the above heat treatment conditionswas achieved and confirmed that the cavity defects were remained. Thatis it was determined that the heat treatment of the present inventionshould be achieved after the wire drawing process to the size of theprobe of the order of 150 μm-300 μm.

Further, it was found that this heat treatment causes the crystalorientation to be significantly coincided with the direction of wiredrawing of the probe and that the etching rate and abrasion rate uponworking the probe tip portion becomes uniform due to this effect,allowing the tip of the probe to be a very smooth flat surface. Thiscauses the probe tip to be difficult to be attached by he oxides,realizing a probe of a good electrical conduction. The surface roughnessof the flat surface may preferably be equal to or less than 0.4 μm.

Also, since the mechanical properties are even (The Young's modulusafter the treatment was 22.3-26.3 kgf/mm² while the Young's modulebefore treatment was 18.8-25.2 kgf/mm².), an excessive over-drive andthe load can be decreased in view of the deviation of the probe by theprobing through the use of the probe card to which the probe isattached.

tensile load Young's modulus × sample gf 103 kgf/mm² before treatment12.800 18.8 12.960 25.2 12.060 18.8 after treatment 13.520 22.3 13.80023.8 13.840 26.3

By using this heat-treated probe material, the probe having the radiusof curvature of the tip of 25 μm according to the first embodiment isused, then the number of times at which the continuous probing for thestable electrical contact resistance is possible was improved ascompared to the first embodiment to more than 200,000 times, resultingin the significant reduction of the test time and costs.

While the description has been made mainly in terms of the probe and theprobe card for testing wafer of the semiconductor integrated circuit,according to the contact method of the present invention, a final testof an electrical conduction can be achieved by the concept of thepresent invention in case of the contact to the lead frame after thesemiconductor integrated circuit is packaged, for example. Also, theprobe can be applied to the operational test of an electronic circuitboard to which a semiconductor integrated circuit or display device orthe like is mounted.

As has been described, according to the semiconductor device test probeof the present invention, the tip portion defining a spherical surfacehas a radius of curvature r expressed by 9t≦r≦35t, where r is the radiusof curvature of the spherical surface and t is the thickness of theelectrode pad, so that the probe tip can efficiently shear and deformthe electrode pad during the probing to establish a sufficientelectrical conduction between the probe tip and the electrode pad,enabling a reliable electrical property test of the semiconductordevice.

Also the tip portion defining a spherical surface has a first curvedsurface substantially positioned in the direction of slippage of theprobe when the probe is urged against the electrode pad and slippedrelative to the electrode pad and a second curved surface opposite tothe first curved surface, and the first curved surface having a radiusof curvature of from 7 μm to 30 μm and larger than that of the secondcurved surface, so that the probe tip can efficiently shear and deformthe electrode pad during the probing to form a small contacting surfacethat establishes a sufficient electrical conduction between the probetip and the electrode pad without the need for the cleaning of the probetip, enabling that the semiconductor device be not damaged and no poorbonding is generated.

Also, the method for manufacturing the semiconductor device test of thepresent invention comprises the steps of roughing the tip portion of thecurved surface by abrasing by means of electrolyte abrasion or abrasingparticles to form a symmetrical spherical curved surface, and finishingthe tip portion by sliding it on an abrasive member comprising anelastically deformable thick film fixed to a substrate and havingabrasive particles therein or thereon directly or through a metallicfilm, so that it is possible to easily manufacture the probe tip thatcan efficiently shear and deform the electrode pad during the probing toform a small contacting surface that establishes a sufficient electricalconduction between the probe tip and the electrode pad without the needfor the cleaning of the probe tip, enabling that the semiconductordevice be not damaged and no poor bonding is generated.

Also, according to the semiconductor device test probe of the presentinvention, the surface roughness of the tip portion of the probe isequal to or less than 0.4 μm, so that the attachment of the oxide to theprobe tip can be prevented and therefore the stable electricalconduction can be continuously maintained.

Also, according to the semiconductor device test probe of the presentinvention, the tip portion of the probe comprises fine grooves extendingin the direction of scrub of the probe against the electrode pads, sothat the attachment of the oxide to the probe tip can be prevented andtherefore the stable electrical conduction can be continuouslymaintained.

Further, the method for manufacturing the semiconductor device testprobe of the present invention comprises the steps of working curvedsurface of the tip portion into a substantially spherical curved surfaceby abrasing by means of electrolyte abrasion or abrasing particles toform a symmetrical spherical curved surface, and inserting or moving thetip portion into the abrasive particles or on a resin including theabrasive particles to form fine grooves extending in the direction ofscrub of the probe against the electrode pads, so that the attachment ofthe oxide to the probe tip can be prevented and therefore the stableelectrical conduction can be continuously maintained.

Also, according to the semiconductor device test probe of the presentinvention, the probe is made of a metallic material made from a powderymaterial, and the probe is heat treated, the heat treatment conditionsbeing a non-oxidizing atmosphere, at the treatment temperature of equalto or less than the recrystallization temperature of the metallicmaterial and the non-oxidizing gas is pressurized, so that the cavitydefects in the probe are decreased and the mechanical property isuniform, the attachment of the oxide to the probe tip can be preventedand therefore the stable electrical conduction can be continuouslymaintained.

Further, according to a semiconductor device of the present invention,the test is achieved by urging the probe against the electrode pad ofthe semiconductor device, providing a relative sliding movement betweenthe probe and the electrode pad to expel the electrode pad material bymaking a lamination stack, so that the generation of the poorwire-bonding can be prevented.

What is claimed is:
 1. A semiconductor device test probe having a tipportion for being urged against an electrode pad of an integratedsemiconductor device to establish an electrical contact between the tipportion and the electrode pad for testing a function of thesemiconductor device: said tip portion defining a spherical surfacehaving a radius of curvature r expressed by 8t≦r≦23t, where r is theradius of curvature of said spherical surface and t is the thickness ofsaid electrode pad.
 2. A semiconductor device test probe having a tipportion for being urged against an electrode pad of an integratedsemiconductor device to establish an electrical contact between the tipportion and the electrode pad for testing a function of thesemiconductor device: said tip portion defining a spherical surfacehaving a first curved surface substantially positioned in the directionof slippage of the probe when the probe is urged against the electrodepad and slipped relative to the electrode pad and a second curvedsurface opposite to said first curved surface; and said first curvedsurface having a radius of curvature of from 7 μm to 30 μm and largerthan that of said second curved surface.
 3. The semiconductor devicetest probe as claimed in claim 1, wherein the surface roughness of saidtip portion of said probe is equal to or less than 0.4 μm.
 4. Thesemiconductor device test probe as claimed in claim 3, wherein said tipportion of said probe comprises fine grooves extending in the directionof scrub of said probe against said electrode pads.
 5. A probe cardhaving a plurality of probes which can be brought into contact with aplurality of electrode pads to test the semiconductor device, whereinthe card comprises the probe of claim
 2. 6. A probe card having aplurality of probes which can be brought into contact with a pluralityof electrode pads to test the semiconductor device, wherein the cardcomprises the probe of claim
 3. 7. A probe card having a plurality ofprobes which can be brought into contact with a plurality of electrodepads to test the semiconductor device, wherein the card comprises theprobe of claim 4.